Looks like you might be going camping, I wouldn't use an inverter, those waste a lot of power through heat and your car might not start at the end of the camping trip unless you keep your car running while charging the battery and even then depending on your alternator, it might not keep up.

I use the Hahnel Unipal charger with my GH2. Can be used with either AC or DC power. It will charge pretty much any digital camera battery as well as AA's and it has a USB charge port as well. Highly recommended.